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The Electromagnetic Spectrum. A Very Short Discussion of Waves. Waves. Waves are pure energy. Waves carry energy from place to place. Examples of waves are Heat Sound Light Water. Characteristics of Waves. All waves have Wavelength ( l ) Amplitude
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The Electromagnetic Spectrum A Very Short Discussion of Waves.
Waves • Waves are pure energy. • Waves carry energy from place to place. • Examples of waves are • Heat • Sound • Light • Water
Characteristics of Waves • All waves have • Wavelength ( l ) • Amplitude • Speed – how fast a crest travels from one place to another. • Frequency – how many waves pass a point in a unit of time.
Electromagnetic Waves The E-M spectrum contains waves that have similar characteristics. These waves do not require a medium and travel at the speed of light. 186,000 miles per hour
Radio Waves • Have the largest wavelengths of all light waves. They can be up to several kilometers long. • Used in Radios, TVs, Communication, and cell phones.
Radio Waves and Astronomy • Space objects emit light at many different wavelengths. • Some of the wavelengths are in the radio wave area of the EM spectrum. • Radio waves are collected by radio telescopes and intrepreted.
Radio Telescopes Parks Radio telescope Very Large Array (VLA) These radio telescopes reflect radio waves into a single focal point where they are collected.
What do radio waves show us? • Different astronomical objects emit different lengths of radio waves. • Scientists can study these emissions in order to learn about the makeup and structure of the universe. CO gases in our milky way galaxy as seen by radio waves
Microwaves • Have wavelengths that can be measured in centimeters • Used in communication, cooking food, sensing, and imaging.
RADAR • An acronym for “radio detection and ranging” • Developed to determine an objects position by firing bursts of microwaves and recording their echo. • Microwaves are able to penetrate haze, clouds, and snow. A radar image from the Space Shuttle.
Cosmic Microwave Background • The universe is constantly giving off microwaves. This phenomenon has been dubbed Cosmic Microwave background. Cosmic Background Explorer (COBE) image
Infrared Radiation • Ranges in size from a single cell to the head of a pin. • Used in imaging, heating food, and remote controls. • Long infrared rays cab be felt as heat, short ones cannot be detected by humans.
How do we see with infrared? • Any object that has a temperature radiates infrared radiation (much in the same way very hot objects will emit visible light)
Making Infrared Pictures • A special camera is used that is able to detect temperature. Each temperature is assigned a different “false color.” Generally, the warmer an object, the more red or orange it is. The colder, the more blue. This is an image of a cat in infrared.
So why use it in Astronomy? • It is easy to study cloud structure. Dark clouds are warmer than light clouds. • We are able to study the effects of urbanization on the earth. What do the red areas represent in this satellite image?
Infrared images can tell us things about space such as the concentration of stars and dust. Image of the Milky Way. The hazy, horizontal S-shaped feature that crosses the image is faint heat emitted by dust in the plane of the Solar System
Visible Light • The only electromagnetic waves we can see. • Their intensities range from red to violet with violet being the highest in energy.
True Color vs False Color • True color—an image that is the same as our eyes would see it. • False color—computers record numbers relating to brightness in another area of the spectrum such as radio waves. The computer then assigns values to these intensities. It is much like color by number!
True Color image of Phoenix, AZ False Color image of Phoenix, AZ
Ultra Violet Radiation • Used in tanning booths, sterilization • Responsible for sun burns and eye cataracts
Ultra Violet Light and Astronomy • Hubble Space telescope uses UV light Satellite image of the sun in ultra violet light.
The hottest and most active objects in the universe give off UV light. Scientists can learn about these objects by studying the amount of UV light given off. False color image of the earth using UV light. Which side of the Earth is facing the sun? How do you know?
Pictures like the one above show which galaxies are new and which ones are old. The top row shows three galaxies in UV light and in visible light in the bottom.
X-Rays • Used in x-ray photographs. • Extremely small wavelength. Extremely high frequency and energy. • The earth’s atmosphere is thick enough that x-rays are not able to penetrate to the surface.
When the Sun shines on us at a certain angle, our shadow is projected onto the ground. Similarly, when X-ray light shines on us, it goes through our skin, but allows shadows of our bones to be projected onto and captured by film.
X-Rays in Astronomy • Astronomers are able to load x-ray detection machines on to satellites. • These satellites are able to detect things like the number of photons collected, the energy of the photons collected, or how fast the photons are detected, can tell us things about the object that is emitting them.
Many things in space emit X-rays, among them are black holes, neutron stars, binary star systems, supernova remnants, stars, the Sun, and even some comets! http://chandra.harvard.edu/ The sun in x-ray
Gamma Rays • Have the smallest wavelength, highest frequency, and highest energy of any other type of electromagnetic radiation. • Generated by radioactive atoms in nuclear explosions. • Produced in the hottest regions of the universe • Things like supernova explosions (the way massive stars die), neutron stars and pulsars, and black holes are all sources of celestial gamma-rays.
